Oil well pump control system



y 1955 M. v. LONG EIAL 2,707,440

OIL WELL PUMP CONTROL SYSTEM Filed July 21, 1951 2 Sheets-Sheet 1' FIG.I

AMPLIHER INVENTORSI M. v. LONG THE-JR ATTORNEY y 3, 1955 M. v. LONG HAL2,707,440

OIL WELL PUMP CONTROL SYSTEM Filed July 21 1951 2 Sheets-Sheet 2 oIIIIIIIIIIII'IIIIIAn-n TEMP.

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M.v LONG F. c. scuuzmak BY: THE-R ATTORNEY United States Patent OIL WELLPUMP CONTRGL SYSTEM Marion V. Long and Frederick Carl Schneider,Berkeley, Calif., assignors to Shell Development Company, Emeryville,Calif., a corporation of Delaware Application July 21, B51, Serial No.237,934

7 Claims. (Cl. 103-25) This invention relates to a system for theeificient production of oil wells and pertains more particularly to anautomatic system for the control of well pumps.

In many wells, especially during the later stages of their exploitation,the quantity of fluid entering the borehole fromthe formation is oftenless than that which can be readily handled by the pumping equipment,that is, the volumetric capacity of the pumping equipment installed atthe well is such that a sustained operation thereof results in pumpingthe well oil or dry. Under these conditions, it is usual to produce suchwells by intermittent pumping, so that the fluid is permitted toaccumulate in the borehole during pump shut-down periods, and isexhausted from the well during alternate pump operation periods.

Such intermittent operation. of the well pumping equipmcnt may becontrolled either manually, whereby the pump is started and stopped byhand for each operating period, or automatically, whereby the pump isstarted and stopped at predetermined set intervals by a time-responsivemechanism, such as an electrically or spring driven clock.

The disadvantages of manual pump control methods, involving thetime-consuming task for a pump operator to visit a great number ofwells, as well as the hazards of the human element, are obvious. Themain disadvantage of most automatic time-responsive mechanisms is thatthey are adjusted to shut oh. and stop the pump after a certain timeinterval. If the time interval is not accurately determined for eachwell, the pumping period may be prematurely cut off at a time whenconsiderable oil remains in the borehole, thus lowering the efficiencyof the pumping operations, or the pumping period may be cut off onlylong after the borehole has been pumped substantially dry, thusincreasing the wear on the pumping equipment and wasting power.

Additionally, many automatic pump control mechanisms employ a swingingor reciprocating check valve in the flow line containing the productionfluid. The movement of the check valve gate is utilized to actuate thepump control mechanism. However, oil, as it is produced from a well,often contains considerable quantities of sand, paraflin or asphalticmaterials which rapidly tend to clog the check valve, and the associatedpump control mechanism soon becomes inoperative.

It is, therefore, an object of the present invention to provide awell-pumping control mechanism which operates efiiciently irrespectiveof the amount of sand, paraflin or other materials present in the streamof production fluid.

It is also an object of this invention to provide a wellpumping controlsystem wherein the duration of the pumping period is automaticallyadjusted to the amount of fluid available for pumping from a well duringsaid pumping period.

It is also an object of this invention to provide a well-pumping controlsystem wherein the operation of the 2,707,440 Patented May 3,. 1955 pumpis automatically stopped when the fluid in the borehole is depleted.

Another object of this invention is to provide a system wherein eachpumping period may be started either by hand or by an automatictime-responsive device, and is terminated by an automatic deviceresponsive to well conditions.

These and other objects of this invention will be understood from thefollowing description taken with reference to the attached drawing,wherein:

Figure 1 is a diagrammatic sketch illustrating the component parts ofthe present system;

Figures 2, 3 and 4 are views, partly in cross-section, of the. flow ortemperature-responsive device of the present system;

Figure 5 is a cross-sectional View of another form of thetemperature-sensing elements of Figure 2;

Figure 6- is a detailed cross-sectional view of the tem perature elementshown in Figure 4, and

Figure 7 is a typical time-temperature curve for oil produced byintermittent pumping of a well.

As shown in Figure l, a pump located in well it) is actuated in a wellknown manner by means of a sucker rodv string 11 the well fluid liftedto the surface being directed to storage through a pipe 12. The suckerrod string 11 is reciprocated in the well by the oscillating motion of awalking beam 13, which is driven, through a pitman l4, crank 15 andspeed reducing mechanism 16, by a prime-mover 17 such as an electricmotor receiving its power through leads 18 and 19. it is understood thatany suitable type of motor or engine may be used as the prime mover 17,such, for example as a gas or gasoline engine having its energizingignition current supplied through leads 18 and 19.

The control circuit of the pump motor 17 may comprise three controlswitches 2t 21 and 22 that are connected in parallel between the motor17 and a power source 23. Switch 2% is a normally-open hand-operatedswitch which, when closed, places the pump 17 in continuous operation.Control switch 21 is normally open being adapted to be closed by atime-responsive device such as an electric or spring driven clockmechanism 24 of any desired type. For simplicity, this mechanism isshown in Figure l as comprising a rotating wheel or disc 25 providedwith a segment 26 adapted to close the switch 21 by contact therewith.It will be seen that the time at which the switch 21 is closed andopened can be accurately pre-set or controlled by suitably adjusting thespeed of rotation of the disc 25 and/or the size of the segment 26.

Control switch 22 is normally closed all the time that fluid is beingpumped from the well borehole and through the delivery line 21.Preferably, switch 22 is small in size, such as a microswitch, or asealed-mercury type switch. The switch 22 is mounted on, and adapted tobe actuated by, a flow-responsive controller device 27 which is in turnconnected to a temperature-sensing element 29 which is mounted on thepipe line 12 in such a manner that a portion of the element is immersedin the flow stream in said line 12.

As shown in Figures 2 to 4, the flow-responsive controller device 27 ofFigure 1 may take many forms. In each case the controller devicecomprises means responsive to the temperature of the fluid flow in thepipe line for closing switch 22 upon cessation of fluid flow throughsaid line. The device, as illustrated in Figure 2, comprises a pair ofpressure bulbs 30 and 31 adapted to contain a pressure fluid or vapor.The bulbs 30 and 31 are in open communication through thermallyinsulated conduits 32 and 33 with a pressure housing 34. The pressurebulbs 30 and 31, conduits 32 and 33, and housing 34 constitute a closedfluid-filled system.

The housing 34 is divided into two chambers 35 and 36 by a flexiblediaphragm 37. A rigid linkage arm 38 1S fixedly attached to thediaphragm 37 and movable therewith, said arm extending through apressure-tight fitting 40 in the wall of the housing 34. The end of thearm as, outside the housing, is adapted to contact terminals 41 and 41aof the electrical switch or relay 22 thus closing or opening said relay22 upon movement of the diaphragm 37. Leads 42 and 42a connect the relay22 into the pump circuit shown in Figure l.

The pressure bulbs 30 and 31 are constructed or arranged in a manner sothat they respond differently to changes in temperature conditions ofthe fluid flow stream. This is accomplished preferably by employingpressure bulbs made of materials having substantially different heatconductivities and/or capacities. For example, if one bulb is made ofcopper and the other of steel, any change in the temperature of thefluid flow stream will change the temperature of the copper bulb at amore rapid rate than the steel bulb.

In the flow controller device illustrated in Figure 2, bulb 30 may be asteel bulb while bulb 31 may be made of copper. With oil at welltemperature flowing through the pipe line 12, the normal position of theswitch 22 is in its closed position, as illustrated in Figures 1 and 2.When the well has been temporarily pumped dry and oil ceases to flowthrough line 12, the vapor or fluid in pressure bulb 31 will cool anddecrease in volume more rapidly than that in bulb 30, causing thediaphragm 37 to move upwardly from its illustrated position. Uponmovement of the diaphragm, arm 38 is also moved so that switch 22 in thepump circuit is opened, thus shutting down the pump. While the pump isshut down, additional oil will drain from the surrounding formationsinto the well borehole. when the pump starting mechanism 24 (Fig. 1)closes switch 21 to start the pump as previously mentioned. As the oilflows past the pressure bulbs 30 and 31, the fluid in the pressure bulb31 will expand more rapidly than that in bulb 30, thus closing switch 22and maintaining it in its closed position as long as oil flows past thebulbs 30 and 31. Hence, even when the segment 26 (Fig. 1) of pumpstarting mechanism 24 has rotated sufficiently far to open switch 21,switch 22 will remain closed and the pump will continue to operate untilthe well has been pumped temporarily dry.

Instead of making the pressure bulbs of different materials in order toobtain a time difference in their responsiveness to temperature changes,the pressure bulbs may be made of the same material if desired as longas the Walls of one bulb are of substantially larger cross-section thanthe walls of the other. The pressure bulbs 30 and 31 will also responddifferently if one is lagged or covered with insulation of low thermalconductivity. While the pressure bulbs 30 and 31 are shown in Figure 2as being axially spaced along the pipe line 12, a pair of fluidfilledpressure bulbs 43 and 44 may also be positioned one within the other asillustrated in Figure 5. In this form the two bulbs may be inserted in asingle well in the pipe 12 with conduits 45 and 46 leading from thebulbs to a pressure chamber similar to the one shown at 34 in Figure 2.

Another form of a pump shut-off device of the present well controlsystem is shown in Figure 3 wherein the flow-sensing element comprises aresistance thermometer 47 positioned in a thermometer well 48 in thepipe line 12. The resistance thermometer forms one arm of a bridgecircuit having two fixed resistance arms 49 and 50 across which isconnected the power source 23. The fourth arm of the bridge comprises avariable resistance 51 which may be set at a value equal to that of theresistance thermometer 47 when no oil is flowing through the pipe 12.Terminals 52 and 53 of the bridge are connected through leads topreferably an amplifier 56 and then the relay 22 in the pump circuit ofFigure 1.

This oil will be subsequently removed In operation, the variableresistance 51 is set at a value about equal to the resistance of theresistance thermometer 47 when no oil is flowing through line 12. Whileoil is flowing through the pipe line 12 the temperature and hence theresistance of the resistance thermometer 47 is increased, unbalancingthe bridge and causing a current to flow therefrom to the amplifier andthe current actuated relay 22 which maintains a normally closed positionas long as current is supplied to it. When the well has pumped dry andthe flow through line 12 has ceased, the resistance of thermometer 47 isdecreased until it equals the setting of variable resistor 51. At thistime the bridge is in balance with no current output to energize relay22. Hence, relay 22 in the pump circuit will open causing the pump to beshut down.

While the device illustrated in Figures 1 and 3 has great utility inmany pumping installations, in other installations the length of timenecessary for the thermometer to cool down to its operative value mayprove to be undesirable. In such case a fluid flow-sensing devicesimilar to that shown in Figure 4 may be employed. In this form of thepresent invention a pair of resistance thermometers 57 and 58 arepositioned in the flow stream of pipe line 12, preferably in a singlethermometer well 61 as shown in Figures 4 and 6.

The resistance thermometers 57 and 58 form two arms of a bridge circuit,the other two arms comprising resistances 59 and 60. The resistancethermometers 57 and 58 are differentially responsive to changes intemperature. Thus, the thermometers may be positioned in two separatethermometer wells made of materials having different thermalconductivity values, or one of the thermometers may be surrounded orcovered with an insulating sheath 62, as shown in Figures 4 and 6.Hence, with a slight change in temperature of one thermometer withrespect to the other, the balance of the bridge is changed thus alteringthe current output from terminals 63 and 64 to the amplifier 56 andrelay 22.

As shown in Figure 4, a normally balanced bridge circuit may be employedtogether with an amplifier 65 and a spring-loaded normally-closed relay66 which opens when the bridge becomes unbalanced in one direction.Preferably, however, the values of the fourresistance arms are arrangedso the bridge circuit is normally slightly unbalanced so that, upon adrop in temperature of oil flowing past the resistance thermometers 57and 58, the bridge becomes balanced with no current output fromterminals 67 and 68 to energize relay 66.

The remainder of the circuit of pump 69 normally comprises a powersupply source 70 for the various com ponents of the system, anormally-closed energized main pump switch or relay 71, and anelectrically or mechanically actuated time-responsive device 76 forclosing relay 71. Preferably, a time-delay relay 72 of any desired typewell known to the art, is also included in the circuit of relay 71.

While the pump circuit may be arranged so that the main switch 71automatically opens when relay 66 be comes deenergized due to a drop intemperature and a stoppage of oil flow in pipe 12, it has been foundthat the temperature of oil pumped from a well may fluctuate for shortperiods. In fact, a time vs. temperature pumping curve for many wellsapproximates the curve shown in Figure 7. Since there is a slight dip atX in the temperature curve shortly after the pumping of oil from a wellhas begun, the pump would be shut off at point X rather than at point Ywhere the well has been pumped dry it a time delay relay 72 is notemployed.

In the operation of the pump circuit shown in Figure 4, a decrease inthe temperature of the oil being pumped, as indicated by the slight dipat X in the curve shown in Figure 7, causes the bridge to becomebalanced and relay 66 deenergized causing its movable member 74 tocontact terminal 75, closing the circuit to the time-delay relay 72which may be of the motor-driven type. In

the well known manner, relay 72 becomes energized and opens terminals72a and 72b after a predetermined period, say five minutes, thusdeenergizing the main pump switch or relay 71 and causing it to open andshut oif the pump. When the temperature of the oil being pumpeddecreases only for a period shorter than that for which the time delayrelay 72 is set, a further increase in the temperature of the oil, asafter point X on the curve, again causes the bridge to becomeunbalanced, and the current output therefrom energizes relay 66 again.

Thus, it is seen that the use of a delay relay 72 in the present circuitpermits the pump to operate in spite of small fluctuations in thetemperature of the oil being pumped. However, a continued drop in thetemperature in the pipe 12, due to the stoppage of the oil flow therein,as shown at point Y on the curve in Figure 7, energizes the time-delayrelay 72 for a sufliciently long period, i. e., over 5 minutes and thepump 69 is thus shut off when the well has been temporarily pumped dry.The pump 69 is again started by closing relay 71 either manually or witha mechanical or electrical time-responsive switch closing device '76, aspreviously described with regard to element 24 in Figure 1. Preferably,the switch-closing device 76 is connected to become electricallyactuated when the pump 69 is shut off. After a predetermined period thedevice 76 closes relay 71.

In the pumping of wells where a drop in temperature of the oil is notlikely to occur until the well has been pumped dry, the time delay relay72 may be left out of the circuit so that the main pump relay 71 isdeenergized and opens to shut oh the pump 69 when there is no ouputcurrent from the balanced bridge due to a drop in temperature when theoil flow stops. While in the preferred form of the invention the bridgecircuit is normally unbalanced, it is understood that the elements ofthe pump circuit could also be arranged to employ a bridge circuit whichis normally balanced when oil is being pumped and becomes unbalanced ona drop in temperature at the end of the pumping period to shut off themain switch 71 in the pump circuit.

We claim as our invention:

1. A control system for a well installation producing a well fluid at atemperature above atmospheric temperature, said system comprising a wellpump, a prime mover for said pump, an energizing electric circuit forsaid prime mover, and conduit means for the fluid delivered by saidpump, said control system comprising first and secondtemperature-sensing means of different thermal responsiveness to changesin temperature of the fluid flow positioned in said conduit means, meansfor comparing the response of said first and second temperature-sensingmeans, and a switch in said electric circuit operated by said comparingmeans to shut off the well pump when the fluid flow in said conduitmeans ceases.

2. A control system for a well installation comprising a well pump, aprime mover for said pump, an energizing electric circuit for said primemover, and conduit means for the fluid delivered by said pump, saidsystem comprising a pair of temperature-sensing means of differentthermal responsiveness positioned in said conduit means, a balancingbridge circuit, said pair of temperaturesensing means forming two armsof said bridge, a pump control circuit connected to said bridge, a firstrelay in said circuit responsive to the state of balance of the bridge,a time delay relay in said control circuit actuated by the operation ofsaid first relay, a normally-closed second relay in said circuitactuated by said time delay relay for shutting off said pump, and atime-responsive device positioned adjacent said second relay foractuating said second relay in the opposite direction to start saidpump.

3. In a well installation comprising a well pump, a prime mover for saidpump and a conduit for the fluid delivered by said pump, the combinationof an energizing electric circuit for said prime mover, two resistancethermometers having diflerent rates of thermal response positioned insaid conduit, a balancing bridge circuit, said two resistancethermometers being connected to form two arms of said bridge circuit, acontrol circuit comprising an amplifier connected to said prime-moverenergizing circuit and to said bridge circuit to apply to saidenergizing circuit the amplified unbalance current appearing across saidbridge circuit, and switch means in said encrgizing circuit actuated bysaid amplified current to deenergize said energizing circuit in responseto a change in the balance of the bridge produced by a predeterminedchange of temperature of the fluid in said conduit.

4. In a well installation comprisin a well pump, a prime mover for saidpump and a conduit for the fluid delivered by said pump, the combinationof an energizing electric circuit for said prime mover, two resistancethermometers having difierent rates of thermal response positioned insaid conduit, a balancing bridge circuit, said two resistancethermometers being connected to form two arms of said bridge circuit, acontrol circuit c0mprising an amplifier connected to said energizingcircuit and to said bridge circuit to apply to said energizing circuitthe amplified unbalance current appearing across said bridge, switchmeans in said energizing circuit actuated by said amplified current todeenergize said energizing circuit in response to a change in thebalance of the bridge produced by a predetermined change of temperatureof the fluid in said conduit, and a time delay relay connected betweenthe amplifier and the switch means in the energizing circuit forretarding the actuation of said switch means by a predetermined timeperiod.

5. In a well installation comprising a well pump, a prime mover for saidpump and a conduit for the fluid delivered by said pump, the combinationof an energizing electric circuit for said prime mover, two resistancethermometers having different rates of thermal response positioned insaid conduit, a balancing bridge circuit, said two resistancethermometers being connected to form two arms of said bridge circuit, acontrol circuit comprising an amplifier connected to said energizingcircuit and to said bridge circuit to apply to said energizing circuitthe amplified unbalance current appearing across said bridge, switchmeans in said energizing circuit actuated by said amplified current todeenergize said energizing circuit in response to a change in thebalance or" the bridge produced by a predetermined change of temperatureof the fluid in said conduit, a time delay relay electrically connectedbetween the amplifier and the switch means .in the energizing circuitfor retarding the actuation of said switch means for a predeterminedtime, and a time-responsive device positioned adjacent said switch meansfor actuating said switch means and energizing said energizing circuitat predetermined intervals.

6. In a well installation comprising a well pump, a prime mover for saidpump and a conduit for the fluid delivered by said pump, the combinationof an energizing electric circuit for said prime mover, a resistancethermometer positioned in said conduit, a balancing bridge circuit, saidresistance thermometer being connected to form an arm of said bridgecircuit, a control circuit comprising an amplifier connected to saidenergizing circuit and to said bridge circuit to appiy to saidenergizing circuit the amplified unbalance current appearing across saidbridge, and switch means in said energizing circuit actuated by saidamplified current to deenergize said energizing circuit in response to achange in the balance of the bridge produced by a predetermined changeof temperature of the fluid in said conduit.

7. A control system for a well installation producing a well fluid at atemperature above atmospheric temperature, said system comprising a wellpump, a prime mover for said pump, an energizing electric circuit forsaid prime mover, and conduit means for the fluid delivered by saidpump, said control system comprising first and secondtemperature-sensing pressure bulbs of different thermal responsivenessto changes in temperature of the fluid flow switch in said electriccircuit actuated by movement of positioned in said conduit means, afluidtight housing, diasaid rod means for shutting off the well pumpwhen the phragm means dividing said housing into a pair of fluidflow offluid from the pump ceases. tight chambers, 21 first conduit incommunication between one of said pressure bulbs and one of saidchambers, 21 5 References Cited in the file of this Patent secondconduit in communication between the other pres- UNHED STATES PATENTSsure bulb and the other chamber, said pressure bulbs,

868,464 Mann Oct. 15, 1907 housing and conduits being filled with apressure fluld, rod 2,550,093 Smith p 24, 1951 means connected to andactuated by said diaphragm means and extending through the wall of saidhousing, and a 10

